Ragweed Parthenium (Parthenium hysterophorus) is a dicot weed in the Asteraceae family. In Colombia this weed first evolved resistance to Group G/9 herbicides in 2004 and infests Fruit. Group G/9 herbicides are known as EPSP synthase inhibitors (Inhibition of EPSP synthase). Research has shown that these particular biotypes are resistant to glyphosate and they may be cross-resistant to other Group G/9 herbicides.

The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

Field, Greenhouse, and Laboratory trials comparing a known susceptible Ragweed Parthenium biotype with this Ragweed Parthenium biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.

Genetics

Genetic studies on Group G/9 resistant Ragweed Parthenium have not been reported to the site. There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature

Mechanism of Resistance

Studies on the mechanism of resistance of Group G/9 resistant Ragweed Parthenium from Colombia indicate that resistance is due to altered translocation. There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature

Relative Fitness

There is no record of differences in fitness or competitiveness of these resistant biotypes when compared to that of normal susceptible biotypes. If you have any information pertaining to the fitness of Group G/9 resistant Ragweed Parthenium from Colombia please update the database.

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Colombia have been instrumental in providing you this information. Particular thanks is given to Cilia Fuentes, and Jesus Ma. Rosario Soccorro for providing detailed information.

Glyphosate has been the most intensely herbicide used worldwide for decades, and continues to be a single tool for controlling weeds in woody crops. However, the adoption of this herbicide in a wide range of culture systems has led to the emergence of resistant weeds. Glyphosate has been widely used primarily on citrus in the Caribbean area, but a study of resistance in the Caribbean islands of Cuba and the Dominican Republic has never been carried out. Unfortunately, Parthenium hysterophorus has developed glyphosate-resistance in both islands, independently. The resistance level and mechanisms of different P. hysterophorus accessions (three collected in Cuba (Cu-R) and four collected in the Dominican Republic (Do-R) have been studied under greenhouse and laboratory conditions. In in vivo assays (glyphosate dose causing 50% reduction in above-ground vegetative biomass and survival), the resistance factor levels showed susceptible accessions (Cu-S ≥ Do-S), low-resistance accessions (Cu-R3 < Do-R4), medium-resistance accessions (Do-R3 < Cu-R2 < Do-R2) and high-resistance accessions (Do-R1 < Cu-R1). In addition, the resistance factor levels were similar to those found in the shikimic acid accumulation at 1000 μM of glyphosate (Cu-R1 ≥ Do-R1 > Do-R2 > Cu-R2 > Do-R3 > Do-R4 > Cu-R3 >> Cu-S ≥ Do-S). Glyphosate was degraded to aminomethylphosphonic acid, glyoxylate and sarcosine by >88% in resistant accessions except in Cu-R3 and Do-R4 resistant accessions (51.12 and 44.21, respectively), whereas a little glyphosate (<9.32%) was degraded in both susceptible accessions at 96 h after treatment. There were significant differences between P. hysterophorus accessions in the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) activity enzyme with and without different glyphosate rates. The R accessions showed values of between 0.026 and 0.21 μmol μg−1 TSP protein min−1 basal EPSPS activity values with respect to the S (0.024 and 0.025) accessions. The same trend was found in the EPSPS enzyme activity treated with glyphosate, where a higher enzyme activity inhibition (glyphosate μM) corresponded to greater resistance levels in P. hysterophorus accessions. One amino acid substitution was found at position 106 in EPSPS, consisting of a proline to serine change in Cu-R1, Do-R1 Do-R2. The above-mentioned results indicate that high resistance values are determined by the number of defense mechanisms (target-site and non-target-site resistance) possessed by the different P. hysterophorus accessions, concurrently..

In Colombia, Parthenium hysterophorus L. has been treated intensively with glyphosate during more than 15 years in fruit orchards. This work was to evaluate the Parthenium response to glyphosate and to confirm the herbicide resistance. Two biotypes of P. hysterophorus seeds were collected in "La Rioja" fruit orchards and in "La Isla" village, next to an irrigation water channel, respectively. "La Rioja" biotype was suspected as resistant; and "La Isla" as susceptible biotype. One experiment dose response was conducted in greenhouse conditions. Were used the doses 0.0, 0.09, 0.72, 1.44, 2.16, 4.32, 6.48 y 8.64 kg de glyphosate ha-1. It was used hazard complete design and hazard completes blocks. We evaluated air biomass fresh weight. It was determined the ED50 and the resistance factor. According to the ED50, the biotype La Rioja needed doses 3.5 times higher than biotype La Isla, for reducing the response in 50% in greenhouse. This is the first report in world about glyphosate resistance of P. hysterophorus..

Glyphosate applications over 15 years in fruit orchards in Colombia, have evolved resistance in Parthenium hysterophorus L. This response could be generated by herbicides absorption and translocation disorders. An assay was carried out in order to study the absorption and translocation of glyphosate and to determine their relationship to resistance diagnosed in P. hysterophorus. 10 µL of a radio labeled solution with 14C-glyphosate (0,464 µCi/mL) was applied on biotype "La Rioja" resistant seedlings with 7-8 leaves and of the susceptible one "La Isla", depositing with a microsyringe 10 drops per leaf on each plant. The activity was measured at 3, 6, 12, 24, 48 and 72 hours after application of the herbicide (H.A.A.). The treatments were distributed in a complete random design. Total penetration, total migration, and migration to other foliar tissues (O.F.T.) and to the roots were calculated. The corresponding statistic analyses were made with the SASTM package. In both biotypes, the absorption of 14C-glyphosate was similar at 72 H.A.A., i.e. 44.9% in the resistant biotype and 48.4% in the susceptible one. However, total migration was different, 21.0% in "La Rioja" resistant and, 26.9% in the susceptible biotype "La Isla". The migration of 14C-glyphosate 24 H.A.A. from the leaf treated to the O.F.T. in the resistant biotype "La Rioja" was two-fold greater than in the susceptible biotype "La Isla". The early migration of the herbicide towards the O.F.T. explains the resistance in P. hysterophorus better than the penetration and total migration..

In fruit orchards of Colombia, Parthenium hysterophorus L has been treated for over 15 years with glyphosate isopropylamine salt (six times a year), but this control is now failing and the evolution of resistance has been suspected. Two experiments were conducted to confirm resistance of P. hysterophorus to glyphosate, and to study the relationship of foliar uptake and translocation with resistance to the herbicide. Seeds of two biotypes were collected from the "La Rioja" fruit orchard, suspected to be resistant and from "La Isla", next to an irrigation water channel, as a susceptible control. Both experiments were carried out in lab and greenhouse. Our investigation confirmed the first case of glyphosate resistance evolution in P. hysterophorus (R.F. 6.23) reported in the world. The 14C-glyphosate translocation behavior was a better explanation of the resistance mechanism than 14Cglyphosate uptake in P. hysterophorus..

Herbicide resistance is an evolutionary event resulting from intense herbicide selection over genetically diverse weed populations. In South America, orchard, cereal and legume cropping systems show a strong dependence on glyphosate to control weeds. The goal of this report is to review the current knowledge on cases of evolved glyphosate-resistant weeds in South American agriculture. The first reports of glyphosate resistance include populations of highly diverse taxa (Lolium multiflorum Lam., Conyza bonariensis L., C. canadensis L.). In all instances, resistance evolution followed intense glyphosate use in fruit fields of Chile and Brazil. In fruit orchards from Colombia, Parthenium hysterophorus L. has shown the ability to withstand high glyphosate rates. The recent appearance of glyphosate-resistant Sorghum halepense L. and Euphorbia heterophylla L. in glyphosate-resistant soybean fields of Argentina and Brazil, respectively, is of major concern. The evolution of glyphosate resistance has clearly taken place in those agroecosystems where glyphosate exerts a strong and continuous selection pressure on weeds. The massive adoption of no-till practices together with the utilization of glyphosate-resistant soybean crops are factors encouraging increase in glyphosate use. This phenomenon has been more evident in Argentina and Brazil. The exclusive reliance on glyphosate as the main tool for weed management results in agroecosystems biologically more prone to glyphosate resistance evolution..